Both schistosomula and adult schistosomes are capable of investing their teguments with host-like antigenic determinants. It is not known whether these antigenic determinants are synthesized by the parasite, are synthesized by the host and incorporated by the parasite, or whether both processes occur simultaneously. One goal of the proposed research is to describe morphological modifications produced in schistosomes by commonly used in vitro culture conditions and to compare these modifications to those produced in an immunologically incompatible host. These modifications will be examined using the techniques of transmission electron microscopy, scanning electron microscopy, and cytochemistry. The data obtained will aid in the elucidation of the cellular processes involved in renewal of surfaces in schistosomes. These studies will also provide a means of assessing the adequacy of various in vitro culture techniques used in other studies, e.g., drug effects, transport mechanisms, or metabolism. The objective of the remainder of the research proposed is to gather information on the capabilities of schistosomes to incorporate and/or synthesize macromolecules. These experiments will utilize radioactive potential surface precursors and the uptake and incorporation of these will be examined. Data obtained from liquid scintillation spectrometry, autoradiography of both soluble and insoluble compounds, and chromatographic identification of products, will be combined to provide information on sites of uptake, sites of incorporation, possible size limitations for uptake mechanisms, and turnover rates of structural components of the surfaces. It is anticipated that the information on the biological capabilities of schistosomes at the cellular level will greatly aid in the understanding of the acquisition of host-like antigenic determinants and of the release of antigens into the host by schistosomes. BIBLIOGRAPHIC REFERENCES: Ernst, Sue Carlisle. 1975. Biochemical and cytochemical studies of esophagus, cecum, and tegument in Schistosoma mansoni: Acid phosphatase and tracer studies. J. Parasitol. 61:633-647. Ernst, Sue Carlisle. 1976. Biochemical and cytochemical studies of alkaline phosphatase activity in Schistosoma mansoni. Clark P. Read Memorial Volume; Rice University Studies (in press).